Method of preparing paper for self-extinguishing cigarettes

ABSTRACT

A method is described for the manufacture of a paper for self-extinguishing cigarettes, by reducing its permeability to air, obtained by applying continuously or onto well defined areas, a composition based on gum Arabic or acacia gum, with or without a fire retardant filler, the application of which is carried out by printing techniques such as serigraphy, heliogravure, flexography or off-set. The concentration of the gum arabic or acacia gum in said composition may vary between 0.15% and 50% by weight, while the amount of product deposited onto the cigarette paper may vary between 0.5 g/m 2  and 10 g/m 2 , by weight.

OBJECT OF THE INVENTION

The present invention refers to a method of preparing paper forself-extinguishing cigarettes, providing essential features of noveltyand important advantages with respect to the processes known and usedfor the same purposes in the current state of the art.

More specifically, the procedure of the invention develops a process bymeans of which a paper for cigarettes is provided with a suitablecoating preferably on its internal face, or face in contact with thetobacco, in areas or continuously, using printing techniques, andobtained from a solution prepared from gum arabic or acacia gum, aloneor in combination with a filler as it is convenient, and with which thepermeability of the paper to air is changed to achieve theself-extinction feature.

The field of application of the present invention includes theindustrial sector dedicated to the manufacture of products to be smokedand especially, of paper for cigarettes.

BACKGROUND AND SUMMARY OF THE INVENTION

Many documents and processes related to the manufacture ofself-extinguishing cigarettes are known in the current state-of-the-art.The endowment of this feature to a cigarette is conventionally obtainedby means of the of the application of some type of coating onto thecigarette paper, intended to modify the air permeability of the paperand in which both the type of the coating applied and its viscosity playan important role in the results obtained.

In order to obtain the above-mentioned goals two methods of treatment ofthe cigarette paper are known, as indicated below:

-   -   1) The first method consists of applying the coating uniformly        onto the entire cigarette paper surface, such that all the paper        has a reduced tendency towards combustion;    -   2) the second method consists of applying the coating on the        surface of the cigarette paper only in previously defined areas,        i.e., to create areas with a reduced capacity of combustion        alternating with others with a normal tendency of combustion.

Within each one of the above-mentioned methods of treatment to obtain apaper adapted to a self-extinguishing cigarette, various methods toobtain the proposed goals may be considered.

The first method (related to a uniformly covered cigarette paper, thatis, with a low on its whole area ignition propensity, has a drawbackthat the air permeability of the paper is low, so that the content oftoxic substances in the smoke is high. Moreover, another drawback ofthis method is that the combustion of cigarettes so manufactured isdeficient: for example, black ashes are produced as well as an unevenand generally thicker than desirable combustion ring.

As of the second method, its main objective consists in reducing the airpermeability of the paper in determined areas only, such that thecombustion in these areas is reduced considerably. This effect may beobtained by different methods, such as, for example, by using a strongcalendaring, by applying specially treated cellulose fibres, or withsubstances melting at a high temperature, by using certain hydrosolubleor liposoluble polymers, etc.

The main object of the present invention, consists in obtaining acigarette paper adapted to the requirements of a self-extinguishingcigarette, by using components that do not affect its taste negativelyand that besides, reduces the possibilities of ignition of the flammablematerials that may enter in contact with it.

This objective has been totally reached achieved with the cigarettepaper obtained by with the process of the present invention and by meansof which the paper is manufactured, preferably on its internal side,with a suitable coating distributed continously or by areas, asconvenient, using printing techniques where the printing “ink” consists,as it has been found extremely beneficial and contrary to the experienceof the previous state-of-the-art, of a solution obtained from gum arabicor acacia gum dissolved in water, with or without fillers added.

On the other hand, it has been determined that the addition of a fireretardant filler to the composition helps to reduce the air permeabilityof the paper, without excessively affecting its viscosity, being themost preferred fire retardant filler those the ones coming from amongthose in the group consisting of aluminium hydroxide, calcium sulphateor magnesium hydroxide.

DESCRIPTION OF A PREFERRED EMBODIMENT

According to the present invention, the procedure allowing thepreparation of a paper for self-extinguishing cigarettes comprisesseveral stages, as explained below.

The first stage of the procedure consists in preparing the compositionthat will be used as the coating, applied continuously or in areas,preferably on the face of the paper in contact with the tobacco. Saidcomposition is obtained by dissolving a predetermined amount of gumArabic or acacia gum in water, in concentrations varying from 0.15% and60% and preferably, between 0.5% and 55%, or even better, between 0.65%and 50%. In practice, the preferred concentration of acacia gum in thecomposition is about 15% to 30%.

If this composition incorporates any fire retardant filler, saidmaterial is added in the second stage of the process, its specificamount depending on its nature. Therefore, suitable amounts of fillerare about 10% aluminum hydroxide, while the rest of the compositionconsists of water until completing 100%.

However, other products exist that may be beneficially combined with gumarabic or acacia gum without excessively affecting its viscosity. Thisis so because of their fire retardant properties and their capability toreduce the air permeability property of the paper, with the subsequentincrease of the self-extinguishing properties of the cigarette.Particularly, these other preferred products may consist of magnesiumhydroxide or calcium sulphate at concentrations comprised within therange of 0.25% to 50%, preferably 2% to 40% and most preferably, 3% to35%.

Once the desired composition or “ink” able to be applied onto thecigarette paper has been manufactured it is applied onto the internalface of the paper, over its total surface area, either by areas oruniformly.

According to the present invention, the composition usable as an “ink”,may be deposited over the cigarette paper by techniques such asserigraphy, heliogravure, flexography or off-set, although it ispreferred to use flexography continuously or in strips, using a transferroller, designed for a correct transfer of the “ink” to the cigarettepaper. According to the invention, this “ink” is to be in a way appliedonto the paper in concentrations ranging from 0.5 g/m² to 10 g/m² ofpaper and preferably from 1.5 g/m² to 9 g/m² of paper and morepreferably from 3 g/m² to 7 g/m² of paper.

Specific factors exist which decisively influence the features of theself-extinguishing paper obtained by applying the aforementionedtechniques, such as the intrinsic characteristics of the base paperused, the nature of the materials applied onto it and the actual amountdeposited.

A very important parameter to be taken into account when printing apaper by any method, is the viscosity of the ink. In heliogravure andflexography, there is a viscosity limit above which the transfer of theink to the contact screen is hindered. Moreover, a high ink viscositycauses a loss of definition of texts and small drawings. Therefore, whenselecting a binder, besides its specific effect of reducing the airpermeability of the paper, its ignition tendency and its influence overcigarette taste, the corresponding limitation of viscosity should alsobe taken into account. As there is a direct relationship between thesolid content of a solution and its viscosity, the viscosity limit isinterpreted as a limit to the solids in the ink and therefore, a limitto the amount of material applied to the paper.

The materials suitable for the present invention consist in a groupcomposed of starch, guar gum, sodium alginate,hydroxypropylmethylcellulose, methylcellulose, sodiumcarboxymethylcellulose and gum arabic or acacia gum.

For purposes of comparison, nitro-cellulose has been evaluated withtriacetine as a plasticizer combined with calcinated kaolin in theTABLE, infra.

Also for purposes of comparison, starch, guar gum, sodium alginate,hydroxypropylmethylcellulose, methyl cellulose, and sodiumcarboxymethylcellulose have been evaluated as set forth in the TABLE,infra.

The ink application system includes the use of rods with differentconcentrations of ink application. These rods apply the ink onto thewire side of the paper, that is to say, the face of the paper to be incontact with the wire of the paper machine upon its production, and itis the face which will be in contact with the tobacco when the cigaretteis manufactured.

A table is shown below which shows the results of the application of theabove-mentioned ink onto the cigarette paper by measuring the airpermeability of the paper before and after applying the ink. The freecombustion of the cigarettes made with standard tobacco, and thecombustion of those cigarettes when in contact with ten sheets oflaboratory filter paper (ash free filter paper, La Papelera de Besós,ref. 438, 15 cm diameter) was measured. The results are as follows:

TABLE Ciga- Initial Final rette Liquid paper paper Free burn amountpermea- permea- ciga- over Concen- applied bility bility rette filterProduct tration % g/m2 UC UC burn paper Reference 1: 10 + 30 7 33 11 YesYes Nitro- cellulose + calcinated Kaolin (Ansilex, Engelhart) Reference2: 32 7 32 3 Yes Yes Nitro- cellulose Starch 4 11 35 28 Yes Yes(Perfectamyl P255, Avebe) Guar gum 2 11 32 22 Yes Yes (Meyprofilm 100,Meyhall) Starch + 3.5 + 0.5 11 35 27 Yes Yes sodium alginate(Perfectamyl P255, Avebe + Satialgine S60, SKW Biosystems) Hydroxypro- 111 32 14 Yes Yes pylmethyl cellulose (Methofas 65HPM450, ICI)Hydroxypro- 2 11 33 9 Yes Yes pylmethyl cellulose (Methofas 65HPM450,ICI) Sodium 2 11 34 14 Yes Yes carboxymethyl cellulose (Finnfix 1500,Noviant) Sodium 6 7 31 0 Yes No carboxymethyl cellulose (Wallocel MW50,Wolff Walsrode). Very high viscosity. Sodium 10 11 35 22 Yes Yescarboxymethyl cellulose (Blanose 7ULC, Hercules). Very high viscosity.Sodium 15 11 35 8 No No carboxymethyl cellulose (Blanose 7ULC, Hercules)Very high viscosity Sodium 7.5 + 7.5 11 34 14 Yes Yes carboxymethylcellulose (Blanose 7ULC, Hercules) + Aluminium hydroxide (Martifin OL107, Martinswerk). High viscosity Sodium 10 + 10 11 35 6 Yes Nocarboxymethyl cellulose (Blanose 7ULC, Hercules) + Aluminium hydroxide(Martinfin OL 107, Martinswerk). High viscosity Sodium 15 + 10 11 32 4Yes No carboxymethyl cellulose (Blanose 7ULC, Hercules) + Aluminiumhydroxide (Martinfin OL 107, Martinswerk). Very high viscosity Sodium10 + 10 11 35 11 Yes No carboxymethyl cellulose (Blanose 7ULC,Hercules) + Magnesium hydroxide. High viscosity Sodium 10 + 10 11 54 14Yes Yes carboxymethyl cellulose (Blanose 7ULC, Hercules) + Magnesiumhydroxide. High viscosity Methyl 2 11 37 11 Yes Yes cellulose (MethocelA15 FG, The Dow Chemical Co.) Methyl 3.7 11 31 7 Yes Yes cellulose(Methocel A15 FG, The Dow Chemical Co.) Methyl 3.7 20 32 2 Yes Yescellulose (Methocel A15 FG, The Dow Chemical Co.) Methyl 3.7 + 3.7 7 324 Yes Yes cellulose + Aluminium hydroxide (Methocel A15 FG, The DowChemical Co. + Martinfin OL 107, Martinswerk) Methyl 3.7 + 3.7 11 32 4Yes Yes cellulose + Aluminium hydroxide (Methocel A15 FG, The DowChemical Co. + Martinfin OL 107, Martinswerk) Methyl 3.7 + 3.7 20 33 2Yes Yes cellulose + Aluminium hydroxide (Methocel A15 FG, The DowChemical Co. + Martinfin OL 107, Martinswerk) Acacia gum. 25.5 11 38 11No No Spray Gum GD Acacia gum. 25.5 11 54 22 Yes No Spray Gum GD Acaciagum 20 + 10 11 54 6 No No Spray Gum GD + Aluminium hydroxide (MartinfinOL 107, Martinswerk)

As it has been said above, inks with high or very high viscositiesimpair the use of the mentioned fillers due to practical reasons.

Likewise, on studying the table it is deduced that, both the type ofmaterial applied onto the cigarette paper and its concentration, are theparameters having the greatest influence in the self-extinction propertyof the cigarettes.

Polymers such as, for example, carboxymethyl cellulose, methylcelluloseor acacia gum are normally used in the cigarette paper and tobaccoindustries as binders for tobacco leaves and papers, as in cigarettepaper booklets, because their application is easy and their effect onthe taste of the cigarette, is small.

In the specific case of arabic or acacia gum, the mixture with aluminiumhydroxide enhances both, an additional reduction of the permeability ofthe paper to air and a reduction of its tendency to burn, even underfree combustion circumstances. The viscosity of a water solution made upof 20% acacia gum and 10% aluminium hydroxide (wt/wt), measured in anumber 4 Ford Cup at room temperature ranges from 40 to 60 seconds.

As it will be understood, the experts in the matter will be able tobring about multiple variations and modifications of the formulationsdescribed in the present invention, without altering the scope of theinvention.

1. A self-extinguishing cigarette comprising tobacco and, as a wrapper,a cigarette paper coated with a fire retardant and an airpermeability-reducing coating, said cigarette paper having (i) anexternal face and (ii) an internal face which is in contact with saidtobacco, characterized in that the coated cigarette paper is producedaccording to a process comprising the steps of: (A) preparing an aqueouscigarette paper coating composition consisting essentially of (I) from0.15% to 60% by weight of acacia gum; (II) from 0.25 to 50% by weight ofa fire-retardant filler which is aluminum hydroxide; and (III) theremainder being water, with the proviso that the concentration offire-retardant filler in the composition is insufficient to cause asubstantial increase in the viscosity of the cigarette paper coatingcomposition; (B) providing an uncoated cigarette paper having aninternal face and an external face; (C) depositing the resulting aqueouscigarette paper coating composition onto the internal face of saiduncoated cigarette paper in a concentration in the range of from 0.5g/m² to 10 g/m² by means of a flexography printing technique in strips.2. The self-extinguishing cigarette of claim 1 wherein in the processfor producing the coated cigarette paper, the aqueous cigarette papercoating composition consists essentially of (I) from 0.5% to 55% byweight of acacia gum; (II) from 0.25% to 50% by weight of aluminumhydroxide and (III) the remainder being water.
 3. The self-extinguishingcigarette of claim 1 wherein in the process for producing the coatedcigarette paper, the aqueous cigarette paper coating compositionconsists essentially of (I) from 0.5% to 55% by weight of acacia gum;(II) from 2% to 40% by weight of aluminum hydroxide and (III) theremainder being water.
 4. The self-extinguishing cigarette of claim 1wherein in the process for producing the coated cigarette paper, theaqueous cigarette paper coating composition consists essentially of (I)from 0.5% to 55% by weight of acacia gum; (II) from 3 to 35% by weightof aluminum hydroxide and (III) the remainder being water.
 5. Theself-extinguishing cigarette of claim 1 wherein in the process forproducing the coated cigarette paper, the aqueous cigarette papercoating composition consists essentially of (I) from 0.65% to 50% byweight of acacia gum; (II) from 0.25% to 50% by weight of aluminumhydroxide and (III) the remainder being water.
 6. The self-extinguishingcigarette of claim 1 wherein in the process for producing the coatedcigarette paper, the aqueous cigarette paper coating compositionconsists essentially of (I) from 0.65% to 50% by weight of acacia gum;(II) from 3% to 35% by weight of aluminum hydroxide and (III) theremainder being water.
 7. The self-extinguishing cigarette of claim 1wherein in the process for producing the coated cigarette paper, theaqueous cigarette paper coating composition consists essentially of (I)from 15% to 30% by weight of acacia gum; (II) from 0.25% to 50% byweight of aluminum hydroxide and (III) the remainder being water.
 8. Theself-extinguishing cigarette of claim 1 wherein in the process forproducing the coated cigarette paper, the aqueous cigarette papercoating composition consists essentially of (I) from 15% to 30% byweight of acacia gum; (II) from 2% to 40% by weight of aluminumhydroxide and (III) the remainder being water.
 9. The self-extinguishingcigarette of claim 1 wherein in the process for producing the coatedcigarette paper, the aqueous cigarette paper coating compositionconsists essentially of (I) from 15% to 30% by weight of acacia gum;(II) from 3% to 35% by weight of aluminum hydroxide and (III) theremainder being water.
 10. The self-extinguishing cigarette of claim 9wherein in the process for producing the coated cigarette paper, theaqueous cigarette paper coating composition is deposited onto saiduncoated cigarette paper in a concentration in the range of from 1.5 to9 g/m².
 11. The self-extinguishing cigarette of claim 9 wherein in theprocess for producing the coated cigarette paper, the aqueous cigarettepaper coating composition is deposited onto said uncoated cigarettepaper in a concentration in the range of from 3 to 7 g/m².
 12. Theself-extinguishing cigarette of claim 10 wherein in the process forproducing the coated cigarette paper, the aqueous cigarette papercoating composition is deposited onto said uncoated cigarette paper bymeans of a flexography printing technique, in strips.
 13. Theself-extinguishing cigarette of claim 11 wherein in the process forproducing the coated cigarette paper, the aqueous cigarette papercoating composition is deposited onto said uncoated cigarette paper bymeans of a flexography printing technique, in strips.
 14. Aself-extinguishing cigarette comprising tobacco and, as a wrapper,cigarette paper coated with a fire retardant and airpermeability-reducing coating, said cigarette paper having (i) anexternal face and (ii) an internal face which is in contact with saidtobacco, characterized in that the coated cigarette paper is producedaccording to the process comprising the steps of: (A) preparing anaqueous cigarette paper coating composition consisting essentially of(I) 20% by weight acacia gum; (II) 10% by weight of aluminum hydroxideand (III) the remainder being water; (B) providing an uncoated cigarettepaper having an internal face and an external face; and (C) depositingthe resulting aqueous cigarette paper coating composition onto theinternal face of said uncoated cigarette paper in a concentration in therange of from 0.5 to 10 gm/m² by means of a flexography printingtechnique, in strips.